Method for a unitary assembly of tubing and a pressed on, interference fit, terminating fitting

ABSTRACT

A unitary assembly of tubing and an end fitting. The end fitting includes a threaded fastener fitting having a tubular bore extending therethrough. A conical transition is coaxially provided to the bore at the thread/hex interface where the bore constricts. The end of the tubing is coaxially impacted, expanded and sized to an external configuration and dimension that achieves an interference fit relative to the tubular bore through the end fitting. The non-expanded end of the tubing is inserted into the larger of the two bores in the end fitting passed the conical transition and through the smaller bore until it experiences interference from the expansion. The interference is overcome by pressing the expansion into the bore in the end fitting until the expansion is completely seated into the end fitting. The expanded tube and end fitting is machined coaxially using a five step tool. The tool machines the inside diameter of the tube where it had been reduced during end forming, swages the expanded tube into the end fitting bore below the hex, machines the female pilot land, machines the O-ring gland, and machines the thread lead on the end fitting.

This application is a division of application Ser. No. 08/155,460, filedon Nov. 19, 1993, now U.S. Pat. No. 5,487,573.

FIELD OF THE INVENTION

This invention relates to tubing connectors and, more particularly, tosuch connectors wherein the terminating fitting is brazed, welded,staked, or extruded onto the associated tube.

BACKGROUND OF THE INVENTION

Tubing connectors for threadless pipe, tubing, conduit and like areknown and have been widely used in the art. The tubes are mechanicallyconnected by means of a threaded fitting which fits over an expansion onthe tube end and are screwed together to clamp the expansion to themating part. These known tubing connectors are exemplified by U.S. Pat.Nos. 2,522,194 and 3,494,643. These known tubing connectors have thedisadvantage of being susceptible to leaking because gaps, inherent tothe design, of significant size occur between the expansion, or flare,and fitting to allow the expansion to deform during assembly. Theresultant deformation allows vibration and the like to loosen thefitting assembly and unseat the sealing surfaces, and repeatedreassembly and sealing to other identical mating components is renderedimpossible.

Tubes that are brazed to fittings via salt, flame, induction, or furnacebraze processes or welded via magnesium inert gas, tungsten inert gas,or resistance welding processes are also known. These known processesare exemplified by U.S. Pat. No. 4,887,853. These known processes havethe disadvantage of using large amounts of energy to heat and coolcomponents, polluting the environment and requiring pre- andpost-treatments and fluxes, all of which are hazardous, and produce abraze or weld joint that forever represents a leak path.

Fittings that are impact extruded onto tubes are known. These knownprocesses have the disadvantage that great expense causes theseprocesses to currently be commercially inviable.

SUMMARY OF THE INVENTION

Briefly, a unitary assembly of tubing with a threaded terminatingfastener is provided. The threaded fitting includes a tubular openingtherein extending through the fitting along the longitudinal axisthereof. A conical constriction is provided at the thread/hex interface.A non-expanded end of an expanded tube is received within the largeropening of the fitting. Insertion continues until expansion and fittinginterference has been overcome and the expansion is completely seated inthe fitting. The internal characteristics are machined coaxially using aspecial five step tool.

The present invention provides a low cost, leak free tube and fittingassembly. This development provides a tube and fitting connectionwithout a potential leak path, such as is present in a braze or weldjoint. The present invention also provides better dimensional andstrength characteristics than a step bead, that may distort in the areaof the O-ring gland and leak. The present invention can be made using apollution free, low tech process that is also less costly than brazing,welding or impact extrusion. The leak free characteristics eliminate theloss of fluid and increases the reliability of products that use tubeand fitting connections. Present technology uses welding, brazing, endforming, or impact extrusion. The first two have inherent leakpotential, the third is structurally and dimensionally inferior and isprone to distortion, and the fourth is expensive.

Other objects, advantages and applications of the present invention willbecome apparent to those skilled in the art when the followingdescription of the best mode contemplated for practicing the inventionis read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIGS. 1 and 2 are sectional and end views respectively of a first hitimpaction of a tube, during an end forming operation according to thepresent invention;

FIGS. 3 and 4 are sectional and end views respectively of a second hitexpansion and the third hit sizing of a tube, during the end formingoperation according to the present invention;

FIGS. 5 and 6 are sectional and end views respectively of a fitting,prior to an assembling operation according to the present invention;

FIGS. 7 and 8 are sectional and end views respectively of the fittingpressed onto the formed end of the tube after the assembling operationaccording to the present invention.

FIGS. 9 and 10 are sectional and end views respectively of the finishedtube and fitting assembly according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 9 and 10, there are shown generally sectional andend views respectively of a finished tube and fitting assembly 10 inaccordance with the present invention. The tube 12 and fitting 14 areconnected along parting line 40. The terminating fitting 14 includes ahexagonal head portion 16 and a threaded connecting portion 18 which isjoined with and coaxially extends away from the head portion 16. Thematerial of the end fitting 14 and tube 12 may comprise any desiredmetallic material, such as aluminum, copper, steel or the like.

Referring now to FIGS. 1 and 2, there are shown sectional and end viewsrespectively of a first hit impaction, which maintains the originaloutside diameter of the tube 12, and coaxially constricts the insidediameter and thickens the wall 20 three fold.

Referring now to FIGS. 3 and 4, there are shown sectional and end viewsrespectively of a second hit expansion, which coaxially expands theimpacted material to an interference fit outside diameter expansionsurface 22 relative to the larger of the two inside diameters of thefitting 14 and rough sizes the inside diameter to a machineablecondition relative to the dimension of the female pilot land 24 of thefinished assembly 10. There is also shown in FIGS. 3 and 4 sectional andend views respectively of a third hit sizing, which sizes the length ofthe end form relative to the transition of the outside diameters and thenon-end formed tube end to provide an exact mating surface 40a to aninside diameter surface 40b and length capability from the hex shoulderto the opposite end. The mating surface 40a of the formed end of thetube 12 and the inside diameter surface 40b of the fitting forming apressed on, interference fit along parting line 40 as illustrated inFIG. 9.

Referring to FIGS. 5 and 6, there are shown sectional and end viewsrespectively of the fitting 14 including the conical transition 26 fromthe major and minor inside diameters 28 and 30 respectively, coaxial tothe threaded and hexagonal portions 18 and 16 respectively.

Referring to FIGS. 7 and 8, there are shown sectional and end viewsrespectively of the tube and fitting assembly which shows the expansionsurface 22 extending beyond the thread lead 32 on the fitting 14 so bothmay be machined simultaneously and the interference fit parting line 40which eliminates any chance that a gap between tube 12 and fitting 14will allow the tube 12 to deform into the fitting 14.

Referring to FIGS. 9 and 10, there are shown sectional and end viewsrespectively of the finished tube and fitting assembly 10 which showsthe constricted portion 34 of the tube 12 is open to the inside diameteralong the entire length of the tube 12, the portion 36 of the tube 12inside the hex 16 swaged into the hex 16, the female pilot land area 24,the O-ring gland 38 and precise mating seam or parting line 40 betweentube 12 and fitting 14.

A method for forming a unitary assembly of tubing with a threadedterminating fastener is therefore disclosed. The method includes thesteps of providing a threaded fitting 14 having a tubular openingtherein extending through the fitting 14 along the longitudinal axisthereof, providing a conical transition 26 at the thread/hex interfacein the fitting 14, providing a tube 12 with a coaxial impacted,expanded, and sized end to an interference dimension relative to theinside diameter of the fitting 14, inserting the non-expanded end of thetube 12 through the major inside diameter of the fitting 14 untilinterference is encountered, pressing the tube 12 into the fitting 14 incoaxial alignment until the fitting 14 is completely seated andfinishing the inside diameter of the tube 12 coaxially with the fitting14 so that the tube inside diameter is consistent over its entirelength, wherein the tube 12 is swaged into the inside of the hex, thefemale pilot land and the O-ring gland are machined, and the overalllength of the fitting 14 is machined concurrently with the tube 12 atthe thread lead. It is believed that the tube and fitting assembly 10 asdescribed above is superior in form, fit, function and costcompetitiveness.

What has been taught, then, is a method and apparatus for providing aunitary assembly of tubing and a terminating fitting facilitating,notably, a pressed-on fitting and which overcomes the disadvantages ofthe prior art. It will be appreciated by those skilled in the art, thatthe present invention provides consistency and reliability of thecompleted connection heretofore deemed unattainable at a marketablecost. The form of the invention illustrated and described herein is buta preferred embodiment of the teachings. It is shown as an illustrationof the inventive concepts, however, rather than by way of limitation,and it is pointed out that various modifications and alterations may beindulged in within the scope of the appended claims.

What is claimed is:
 1. A method for forming a unitary assembly of tubing with a threaded terminating fastener comprising the steps of:providing a threaded fitting having a tubular opening therein extending through said fitting along a longitudinal axis thereof and an enlarged major inside diameter opening adjacent one end thereof; providing a tube having an enlarged diameter portion adjacent one end thereof; inserting said tube through said enlarged major inside diameter opening of said threaded fitting; and press fitting said enlarged diameter portion of said tube with an interference fit within said enlarged major inside diameter opening of said threaded fitting.
 2. The method of claim 1 further comprising the steps of:impacting an end of said tube to increase a wall thickness by approximately three fold; expanding said end of said tube having said thickened wall; and sizing said expanded end of said tube to desired coaxial minor and major diameters with a conical transition therebetween sufficient to provide interference fit with said enlarged major diameter opening of said fitting.
 3. The method of claim 1 further comprising the steps of:inserting a non-expanded end of said tube through said enlarged major inside diameter opening of said fitting until interference is encountered; and pressing said tube into said fitting in coaxial alignment until said fitting is completely seated.
 4. The method of claim 1 further comprising the step of finishing an inside diameter of said tube coaxially with said fitting so that an inside diameter of said tube is substantially constant over a longitudinal length.
 5. The method of claim 1 further comprising the step of machining a female pilot land on an exposed end of the unitary assembly of tubing and fastener.
 6. The method of claim 1 further comprising the step of machining an O-ring gland on an exposed end of the unitary assembly of tubing and fastener.
 7. The method of claim 1 further comprising the step of machining an overall length of said unitary assembly of tubing and fastener.
 8. A method for forming a unitary assembly of tubing with a threaded terminating fastener, said method comprising the steps of:providing a threaded fitting having a tubular opening therein extending through said fitting along a longitudinal axis thereof, said tubular opening having coaxial minor and major inside diameters with a coaxial conical transition therebetween at a thread/hex interface of said fitting; providing a tube with a coaxial impacted, expanded, and sized end to an interference dimension relative to an inside diameter of said fitting; inserting a non-expanded end of said tube through said major inside diameter of said fitting until interference is encountered; pressing said tube into said fitting in coaxial alignment until said fitting is completely seated; finishing an inside diameter of said tube coaxially with said fitting so that an inside diameter of said tube is substantially constant over a longitudinal length; and machining a female pilot land, an O-ring gland and an overall length of said fitting on an exposed end of said unitary assembly of tubing and fastener.
 9. A method for forming a unitary assembly of tubing with a terminating fastener comprising the steps of:providing a fitting having a tubular opening therein extending through said fitting along a longitudinal axis thereof and an enlarged major inside diameter opening adjacent one end thereof; providing a tube having an enlarged diameter portion adjacent one end thereof; inserting said tube through said enlarged major inside diameter opening of said fitting; and press fitting said enlarged diameter portion of said tube with a face-to-face interference fit within said enlarged major inside diameter opening of said fitting.
 10. The method of claim 9 further comprising the steps of:impacting an end of said tube to increase a wall thickness by approximately three fold; expanding said end of said tube having said thickened wall; and sizing said expanded end of said tube to desired coaxial minor and major diameters with a conical transition therebetween sufficient to provide face-to-face interference fit with said enlarged major diameter opening of said fitting.
 11. The method of claim 9 further comprising the steps of:inserting a non-expanded end of said tube through said enlarged major inside diameter opening of said fitting until interference is encountered; and pressing said tube into said fitting in coaxial alignment until said fitting is completely seated.
 12. The method of claim 9 further comprising the step of finishing an inside diameter of said tube coaxially with said fitting so that an inside diameter of said tube is substantially constant over a longitudinal length thereof.
 13. The method of claim 9 further comprising the step of machining a female pilot land on an exposed end of the unitary assembly of tubing and fastener.
 14. The method of claim 9 further comprising the step of machining an O-ring gland on an exposed end of the unitary assembly of tubing and fastener.
 15. The method of claim 9 further comprising the step of machining an overall length of said fitting on an exposed end of the unitary assembly of tubing and fastener. 